KS-18L/XL modified light

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for some time I was thinking how to improve my KS-18L light. In general it's a great light, but in my opinion it suffers from two limitations:

Light beam is very narrow, causing objects just ahead invisible.

Light is not adjustable, especially there is no way to tilt the beam down other than recalibration of the entire wheel.

So I decided do design slightly modified lamp PCB and here it is:

There are two versions - with and without additional LEDs. Two additional LEDs are for to illuminate the road directly in front of the wheel (they fill the black area below the main light beam). New PCBs are made of four layers of 70 um copper onto FR4 1 mm substrate. This stackup should be able to conduct heat well enough that when combined with additional heatsinks (not shown on photo above).

Improvements over original

newer and brigher Cree XP-G3 diode in place of original XP-G2

best light color of 5000 K (original is much colder)

additional LEDs to extend beam to the bottom

stronger and slightly higher red light

slightly lowered beam

board can be adjusted to lower beam by another few degrees

Lamp modification doesn't require any skills other than screwdriwer operation Modified lamp board is mounted in place of original one, no slighest modifications required.

Test results - front light

All photos below are made with the same settings (ISO, shutter, aperture and white balance).

A. Original KS-18XL lamp.

B. Original KS-18L lamp.

C. Modified KS-18L (without additional LEDs).

D. Modified KS-18L (with additional LEDs).

Test results - rear light

A. Original KS-18L lamp.

B. Modified KS-18L lamp.

Of course it needs more field testing, but first results are very promising. Especially filling the area below the main beam seems to be working as intended. Of course upper beam will be slightly less intensive, but it's a fair trade-off. Even without these LEDs modified board seems to be superior to the original one in terms of light quality. Beam is slightly tilted down, wider and much brighter. Light color is much more eye-friendly, with better color rendering. Red light is also stronger and filled better.

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Looking forward to hearing the news after that test ride.
Will you be selling them? Depending on the price I may buy one or two.
I suggest you also do a version with only red light, no white light, as it may save in cost and most people don't need the white light on the back, it always being red is better, not changing (it would sometimes change when I'm stopped at a red light, probably blinding people behind me as the unit is tilted forward, well not anymore, as I've put the one with the broken white led behind)

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So, I've found that the new light works especially well when going downhill. Now the lower beam of light illuminates the road ahead that was previously lost in the darkness. The main beam of light illuminates the trunks of trees, nothing has changed here - as expected. Main beam isn't as bright as in original, because of splitting the electric power between two beams. It's still bright enough.

Here is the photo from riding down the bikepath on the 7 % hill. The light ahead is the lower beam. With factory light this bike path would not completely off-light.

6 hours ago, Jean Dublin said:

Will you be selling them? Depending on the price I may buy one or two.﻿﻿

I consider selling the boards, but first I have to test it thoroughly to be sure they works as expected. Maybe there will be also some modifications, because I'm not fully satisfied for now. Especially there is a gap between lower and main beam I would like to remove and to slightly tilt up the lower beam.

6 hours ago, Jean Dublin said:

I suggest you also do a version with only red light, no white light, as it may save in cost and most people don't need the white light on the back, it always being red is better, not changing (it would sometimes change when I'm stopped at a red light, probably blinding people behind me as the unit is tilted forward, well not anymore, as I've put the one with the broken white led behind)﻿﻿﻿

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@Seba I like what you are trying to do here, but I think the main problem with all EUC headlights is not the LED but the shape of the reflector, and the lack of design in the front "lens". They all seem to be borrowed from flashlight technology, and a flashlight simply throws a round beam with no correction for traffic considerations; relying on the operator to aim and adjust the beam by hand, as necessary. Profiling the reflector and or light correcting redesign of the "lens" ( which is currently simply a flat piece of clear plastic) seems to be the way to go

Edited February 1 by Smoother

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@Seba I like what you are trying to do here, but I think the main problem with all EUC headlights is not the LED but the shape of the reflector, and the lack of design in the front "lens". They all seem to be ﻿borrowed from flashlight technolo﻿gy, and a flashlight simply throws a ro﻿und be﻿am﻿ with n﻿o corre﻿﻿ction for tr﻿a﻿ffic considerations; relying on the operator to aim and adjust the beam by hand, as necessary. Profiling the reflector and or light correcting redesign of the "lens" ( which is currently simply a flat piece of clear plastic).

In case of KS-18L/XL there is no need for lens, because of specially shaped reflector. This is the main optical part that takes major role in shaping the light beam. And in this particular case this reflector works very well. It even works too good, creating very sharp and too narrow beam. What I try to do is to relocate the LED from the reflector focal point, to "defocus" the light beam and pull it down slightly. Two additional LEDs are for creating additional, low beam to better light the area just ahead. As you can see on the photos above, original light that is projected onto the garage door isn't circular. It is rectangular in shape. When riding on even, horizontal road with some speed, it lights the road very good without blinfing oncoming traffic (of course if the wheel is properly calibrated).

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In case of KS-18L/XL there is no need for lens, because of specially shaped reflector. This is the main optical part that takes major role in shaping the light beam. And in this particular case this reflector works very well. It even works too good, creating very sharp and too narrow beam. What I try to do is to relocate the LED from the reflector focal point, to "defocus" the light beam and pull it down slightly. Two additional LEDs are for creating additional, low beam to better light the area just ahead. As you can see on the photos above, original light that is projected onto the garage door isn't circular. It is rectangular in shape. When riding on even, horizontal road with some speed, it lights the road very good without blinfing oncoming traffic (of course if the wheel is properly calibrated).

First let me say, that you have my respect for a) your technical skills (i've read all your posts about the 18L trolley problems) and b) your desire to try and improve a poor EUC design. Now for my thoughts:

So you are trying to improve a specially shaped reflector that works very well. I suggest that while the first statement is true (It isn't simply cone shaped), the latter is false, otherwise there would be no need to to make it work properly.

Do you have access to a 3D printer? Maybe printing a new reflector, contoured properly, might produce better results; assuming that a suitable reflective surface could be created.

What about heating the existing reflector and molding it into a better shape?

To tell the truth, I couldn't see much difference in your before and after pictures, and I went back and forth several times.

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So you are trying to improve a specially shaped reflector that works very well. I suggest that while the first statement is true (It isn't simply cone shaped), the latter is false, otherwise there would be no need to to make it work properly.

The point is that I don't want to improve reflector. I'm trying to improve the lamp as a whole I can do this by either modifying the reflector (what is not the case) or the light source (what I'm trying to do). Of course I understand that there is a limited space for modifications.

1 hour ago, Smoother said:

To tell the truth, I couldn't see much difference in your before and after pictures, and I went back and forth several times. ﻿

It's hard to make a comparision inside a tiny garage by projecting the light onto the garage door And I agree, differences are not spectacular. The most important change is to defocus the main beam, tilt it slightly down and add some additional light into the previously dark spot below the light beam.

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Since you have a "lot" of free space around the lower side of the board (near the, I guess, power resistor), you could also possibly add a PWM-circuit with something like a small SMD potentiometer there to adjust the light power? Not sure how much of real world use it would be though (does anyone really want to have a less bright light?) Unless using a smaller resistor for the LED itself, not sure how much the LED lifetime drops if it's being PWM'd with current above the ratings...

Edited January 31 by esaj

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Since you have a "lot" of free space around the lower side of the board (near the, I guess, power resistor), you could also possibly﻿ add a PWM﻿-circuit with something like a small SMD potentiometer there to adjust the light power? Not sure how much of real world use it﻿ would be﻿ though (does anyone really want to have a less bright light?) Unless using a smaller resistor for the LED itself, not sure how much the LED lifetime drops if it's being PWM'd with current above the ratings...

This is not power resistor, it's resettable PTC fuse with rated current of 750 mA. To be honest I don't know why KS used this in the lamp PCB... Anyway, I decided to add this fuse too. However, white LED is driven by current source with 700 mA. In this situation adding additional circuitry would interfere with this current source, so I left it as is. Additional problem is the limited space to dissipate heat. Early KS boards suffered from insufficient heat dissipation, what caused the LEDs to overheat and fail after few months of use. This is why there is a free space you see

I initially thought that the both leds - white and red - are PWM driven. In fact only red LED is driven with PWM, white one is powered from 700 mA constant current source. Nominal power of while LED is 2 Watts.

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This is not power resistor, it's resettable PTC fuse with rated current of 750 mA. To be honest I don't know why KS used this in the lamp PCB... Anyway, I decided to add this fuse too. However, white LED is driven by current source with 700 mA. In this situation adding additional circuitry would interfere with this current source, so I left it as is. Additional problem is the limited space to dissipate heat. Early KS boards suffered from insufficient heat dissipation, what caused the LEDs to overheat and fail after few months of use. This is why there is a free space you see

I initially thought that the both leds - white and red - are PWM driven. In fact only red LED is driven with PWM, white one is powered from 700 mA constant current source. Nominal power of while LED is 2 Watts.

Ah, ok, I thought there'd just be separate power lines for the white and red LEDs, and current limitation through a simple resistor. Guess they added the PTC in case the LEDs fail in short circuit, just in case it might otherwise destroy the constant current source/sink?

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for some time I was thinking how to improve my KS-18L light. In general it's a great light, but in my opinion it suffers from two limitations:

Light beam is very narrow, causing objects just ahead invisible.

Light is not adjustable, especially there is no way to tilt the beam down other than recalibration of the entire wheel.

So I decided do design slightly modified lamp PCB and here it is:

There are two versions - with and without additional LEDs. Two additional LEDs are for to illuminate the road directly in front of the wheel (they fill the black area below the main light beam). New PCBs are made of four layers of 70 um copper onto FR4 1 mm substrate. This stackup should be able to conduct heat well enough that when combined with additional heatsinks (not shown on photo above).

Improvements over original

newer and brigher Cree XP-G3 diode in place of original XP-G2

best light color of 5000 K (original is much colder)

additional LEDs to extend beam to the bottom

stronger and slightly higher red light

slightly lowered beam

board can be adjusted to lower beam by another few degrees

Lamp modification doesn't require any skills other than screwdriwer operation Modified lamp board is mounted in place of original one, no slighest modifications required.

Test results - front light

All photos below are made with the same settings (ISO, shutter, aperture and white balance).

A. Original KS-18XL lamp.

B. Original KS-18L lamp.

C. Modified KS-18L (without additional LEDs).

D. Modified KS-18L (with additional LEDs).

Test results - rear light

A. Original KS-18L lamp.

B. Modified KS-18L lamp.

Of course it needs more field testing, but first results are very promising. Especially filling the area below the main beam seems to be working as intended. Of course upper beam will be slightly less intensive, but it's a fair trade-off. Even without these LEDs modified board seems to be superior to the original one in terms of light quality. Beam is slightly tilted down, wider and much brighter. Light color is much more eye-friendly, with better color rendering. Red light is also stronger and filled better.

I always appreciate the fact that you use your technical expertise to think of new and functional ways to improve EUC design. That's positive. Keep it moving. What EUC problem will Seba tackle next 🤔🤔🤔🤔🤔? Stay tuned. 😉👍

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I consider selling the boards, but first I have to test it thoroughly to be sure they works as expected. Maybe there will be also some modifications, because I'm not fully satisfied for now. Especially there is a gap between lower and main beam I would like to remove and to slightly tilt up the lower beam.